Aggregation and continuous π-stacking have been the major obstacles hindering the fluorescence (FL) quantum yield (ΦF) of perylene diimide (PDI) derivatives in the condensed phase. To prepare polymer microspheres with nearly unity ΦF, in this work a POSS functionalized PDI derivative, POSS-PDI-POSS (PPP), was applied as the red fluorophore of poly(3-hydroxylbutyrate-co-3-hydroxyvalerate) (PHBV) and polystyrene (PS) microspheres. The electrosprayed PPP/PHBV and PPP/PS microspheres have unique hollow structures. Moreover, they show bright red FL under a fluorescence microscope. A photophysical study of the microspheres indicates a significant role of the polymer matrix in disrupting the aggregation state and the ΦF of the embedded PPP fluorophore. Both the PPP/PHBV and the PPP/PS microspheres show higher ΦF than most PDI materials in the condensed phase. The PPP/PHBV microspheres show ΦF of 28%, whereas the PPP/PS microspheres give nearly unity ΦF.